Supercharged internal combustion engine with cooled exhaust-gas recirculation arrangement

ABSTRACT

Methods and systems are provided for a cooling arrangement. In one example, a method for the cooling arrangement may comprise adjusting exhaust-gas recirculate and/or exhaust gas flow to first and second coolers of the cooling arrangement in response to one or more of an exhaust-gas recirculate demand and an energy recovery demand.

CROSS REFERENCE TO RELATED APPLICATION

The present application claims priority to German Patent Application No.102016218990.5, filed Sep. 30, 2016. The entire contents of theabove-referenced application are hereby incorporated by reference in itsentirety for all purposes.

FIELD

The present description relates generally to methods and systems forcontrolling a combined low-pressure exhaust gas recirculation (LP-EGR)and heat recovery system with EGR cooling and heat recoveryfunctionality.

BACKGROUND/SUMMARY

An internal combustion engine of the stated type is used as a motorvehicle drive unit. Within the context of the present disclosure, theexpression “internal combustion engine” encompasses diesel engines andOtto-cycle engines and also hybrid internal combustion engines, whichutilize a hybrid combustion process, and hybrid drives which comprisenot only the internal combustion engine but also an electric machinewhich can be connected in terms of drive to the internal combustionengine and which receives power from the internal combustion engine orwhich, as a switchable auxiliary drive, additionally outputs power.

In the development of internal combustion engines, it is sought tominimize fuel consumption. Furthermore, a reduction of the pollutantemissions is sought in order to be able to comply with future limitvalues for pollutant emissions.

Internal combustion engines are ever more commonly being equipped withsupercharging, wherein supercharging may be a method for increasingpower, in which the charge air used for the combustion process in theengine is compressed, as a result of which a greater mass of charge aircan be supplied to each cylinder per working cycle. In this way, thefuel mass and therefore the mean pressure can be increased.

Supercharging is a suitable means for increasing the power of aninternal combustion engine while maintaining an unchanged swept volume,or for reducing the swept volume while maintaining the same power. Inany case, supercharging leads to an increase in volumetric power outputand a more expedient power-to-weight ratio. If the swept volume isreduced, it is possible, given the same vehicle boundary conditions, toshift the load collective toward higher loads, at which the specificfuel consumption is lower. Supercharging of an internal combustionengine consequently assists in the efforts to minimize fuel consumption,that is to say to improve the efficiency of the internal combustionengine.

By means of a suitable transmission configuration, it is additionallypossible to realize so-called downspeeding, whereby a lower specificfuel consumption is likewise achieved. In the case of downspeeding, useis made of the fact that the specific fuel consumption at low enginespeeds is generally lower, in particular in the presence of relativelyhigh loads.

With targeted configuration of the supercharging, it is also possible toobtain decreased exhaust-gas emissions. With suitable supercharging forexample of a diesel engine, the nitrogen oxide emissions can thereforebe reduced without any losses in efficiency. At the same time, thehydrocarbon emissions can be positively influenced. The emissions ofcarbon dioxide, which correlate directly with fuel consumption, likewisedecrease with falling fuel consumption.

To adhere to future limit values for pollutant emissions, however,further measures are desired. Here, the focus of the development work ison inter alia the reduction of nitrogen oxide emissions, which are ofhigh relevance in particular in diesel engines. Since the formation ofnitrogen oxides occurs not only an excess of air but also hightemperatures, one concept for lowering the nitrogen oxide emissionsconsists in using combustion processes with lower combustiontemperatures.

Here, exhaust-gas recirculation (EGR), that is to say the recirculationof combustion gases from the outlet side to the inlet side of an engine,is expedient in achieving this aim, wherein it is possible for thenitrogen oxide emissions to be considerably reduced with increasing EGRrate. Here, the EGR rate x_(EGR) is determined asx_(EGR)=m_(EGR)/(m_(EGR)+m_(fresh air)), where m_(EGR) denotes the massof recirculated exhaust gas and m_(fresh air) denotes the supplied freshair. The oxygen provided via exhaust-gas recirculation may possibly betaken into consideration.

To obtain a considerable reduction in nitrogen oxide emissions, high EGRrates may be desired, which may be of the order of magnitude ofx_(EGR)≈60% to 70% or more. Such high recirculation rates may demandcooling of the EGR, by which means the temperature of the exhaust gas isreduced and the density of the exhaust gas increased, so that a greatermass of exhaust gas can be recirculated. Consequently, an exhaust-gasrecirculation arrangement is commonly equipped with a cooler. Theexhaust-gas recirculation arrangement of the internal combustion engineto which the present disclosure relates also has a cooling arrangement,that is to say at least one EGR cooler, which has a coolant-conductingcoolant jacket which serves for the transfer of heat between exhaust gasand coolant.

Problems can arise during the introduction of the recirculated exhaustgas into the intake system if the temperature of the recirculated hotexhaust gas decreases and condensate forms.

Firstly, condensate can form if the recirculated hot exhaust gas meets,and is mixed with, cool fresh air in the intake system. The EGR gascools down, whereas the temperature of the fresh air is increased. Thetemperature of the mixture of fresh air and EGR, that is to say thetemperature of the combustion air, lies below the temperature of theEGR. During the course of the cooling of the exhaust gas, liquidspreviously contained in the EGR and/or in the combustion air still ingaseous form, in particular water, may condense if the dew pointtemperature of a component of the gaseous combustion-air flow isundershot. Condensate formation occurs in the free combustion-air flow,wherein contaminants in the combustion air often form the starting pointfor the formation of condensate droplets.

Secondly, condensate can form when the EGR and/or the combustion airimpinges on the internal wall of the intake system, as the walltemperature generally lies below the dew point temperature of therelevant gaseous components.

Condensate and condensate droplets are undesirable and may to increasednoise emissions in the intake system and possibly to degradation of theimpeller blades of a compressor impeller, which is arranged in theintake system, of a supercharger or of an exhaust-gas turbocharger. Thelatter effect is associated with a reduction in efficiency of thecompressor.

With regard to the problem of the above-described condensate formation,too, an EGR cooler may be expedient or helpful. The cooling of theexhaust gas for recirculation during the course of the recirculation hasthe effect that the condensate does not form for the first time in theintake system but forms already during the recirculation, and can beseparated off during the course of the recirculation.

A disadvantage of the EGR coolers according to previous attempts is thatthe useful exhaust-gas energy, that is to say the heat that can beextracted from the exhaust gas in the cooler by means of coolant, is outof principle only available and usable when exhaust gas is beingrecirculated. According to the previous examples, if the exhaust-gasrecirculation arrangement has been deactivated, such that no exhaust gasis being recirculated, the exhaust-gas energy of the hot exhaust gas maybe wasted. If it were possible to utilize said exhaust-gas energy, thatis to say to recover said exhaust-gas energy in the context of energyrecovery, it would be possible to achieve further efficiency advantagesin the internal combustion engine.

The energy of the hot exhaust gas could for example be utilized toreduce the friction losses and thus the fuel consumption of the internalcombustion engine. Here, rapid warming of the engine oil by means ofexhaust-gas heat, in particular after a cold start, could be expedient.Fast warming of the engine oil during the warm-up phase of the internalcombustion engine ensures a correspondingly fast decrease in theviscosity of the oil and thus a reduction in friction and frictionlosses, in particular in the bearings which are supplied with oil, forexample the bearings of the crankshaft.

Here, the oil could for example be actively warmed by means of a heatingdevice. For this purpose, it is possible in the warm-up phase for acoolant-operated oil cooler to be utilized, contrary to its intendedpurpose, for cooling the oil.

Fast warming of the engine oil in order to reduce friction losses maybasically also be aided by means of fast heating of the internalcombustion engine itself, which in turn is assisted, that is to sayforced, by virtue of as little heat as possible being extracted from theinternal combustion engine during the warm-up phase.

In this respect, in the case of a liquid-cooled internal combustionengine, it may also be expedient for heat to be supplied to the coolantof the engine cooling arrangement, in particular in the warm-up phase orafter a cold start. It would be possible for the exhaust-gas energy tobe utilized for warming the coolant of the engine cooling arrangement.

It is also a disadvantage of EGR coolers according to the previousattempts that the coolers may not be configured to perform energyrecovery, with the focus rather being on the cooling of the exhaust gas,that is to say the pure cooling effect. Here, the cooler may be able tocope with all exhaust-gas flow rates for recirculation via theexhaust-gas recirculation arrangement during the operation of theinternal combustion engine. In particular, the maximum exhaust-gas flowrate for recirculation and for cooling may be allowed for. The range ofvariation of the exhaust-gas flow rate for recirculation via theexhaust-gas recirculation arrangement leads to widely varying pressureconditions at the cooler. The pressure gradient across the coolerchanges noticeably in a manner dependent on the exhaust-gas flow ratefor recirculation, that is to say in such a relevant manner that it maybe taken into consideration in the control or setting of therecirculation rate. The resulting interaction leads to certain dynamics,and necessitates correspondingly complex or intricate control of theexhaust-gas recirculation arrangement.

In one example, the issues described above may be addressed by asupercharged internal combustion engine having at least one cylinder, anintake system for supplying air to the at least one cylinder, anexhaust-gas discharge system for discharging the exhaust gases, and anexhaust-gas recirculation arrangement which comprises at least onerecirculation line, with at least one cooler and at least one controlelement being provided in the at least one recirculation line for thepurposes of setting a predefinable exhaust-gas flow rate forrecirculation, the internal combustion engine further comprising atleast two recirculation lines, in which there is arranged in each caseone cooler, the coolers being arranged in parallel and being usableindependently of one another for cooling exhaust gas for the purposes ofenergy recovery.

In the case of the internal combustion engine according to thedisclosure, multiple coolers are provided by means of which exhaust gasfor recirculation can be cooled. In some cases, the coolers can beactivated, and used for the cooling of exhaust gas for recirculation,simultaneously. In this way, the cooling power of the EGR coolingarrangement, or the number of EGR coolers, can be adapted to theexhaust-gas flow rate for cooling. The benefits of which will bedescribed in greater detail below.

The pressure gradient across a single cooler changes during theoperation of the cooler to a lesser extent than in the previousexamples, because the exhaust-gas flow rates to be cooled or coped withby said cooler vary to a lesser extent.

In the case of relatively low recirculation rates, it is possibleaccording to the disclosure for one cooler to be used for cooling theexhaust gas for recirculation. If the exhaust-gas flow rate forrecirculation and for cooling then increases, it is possible, forexample in the event of an exceedance of a predefinable exhaust-gas flowrate, for a further cooler to be activated in order to cool exhaust gasand contribute to the cooling of the exhaust gas for recirculation.Depending on the number of EGR coolers provided, if for example three,four or more coolers are provided, activation can be performed severaltimes or in succession. The control or adjustment of the recirculationrate reacts less dynamically.

Furthermore, the line system of the exhaust-gas-conducting lines may beconfigured or switchable in such a way that, even when the exhaust-gasrecirculation arrangement has been deactivated, when no exhaust gas isbeing recirculated, one cooler is utilized and used for cooling exhaustgas, such that, by contrast to the previous examples, the energyinherent in the exhaust gas can be utilized, or made utilizable, in thecontext of energy recovery even when the exhaust-gas recirculationarrangement has been deactivated.

The exhaust-gas energy can be utilized for example in the warm-up phaseor after a cold start for warming the engine oil of the internalcombustion engine and thus reducing the friction losses of the internalcombustion engine. In the case of a liquid-cooled internal combustionengine, the exhaust-gas energy can be utilized for warming the coolantof the engine cooling arrangement and thus accelerating the heating ofthe internal combustion engine. Both measures improve or increase theefficiency of the internal combustion engine.

The EGR coolers of the internal combustion engine according to thedisclosure are configured both with regard to effective cooling and withregard to the energy recovery, that is to say the utilization of theexhaust-gas energy. According to the disclosure, both aspects areprovided.

The internal combustion engine to which the present disclosure relatesis a supercharged internal combustion engine. Reference is made to thebenefits already mentioned, and the statements made, in conjunction withsupercharging.

The internal combustion engine according to the disclosure thus may be asupercharged internal combustion engine where the exhaust-gas energy canbe utilized more effectively than in the previous examples, and which isfurther improved with regard to the exhaust-gas recirculation.

According to the disclosure, the at least two recirculation lines belongto one exhaust-gas recirculation arrangement, that is to say to asingle, or the same, exhaust-gas recirculation arrangement. An internalcombustion engine which is equipped with a low-pressure EGR arrangementcomprising a recirculation line and with a high-pressure EGR arrangementcomprising a recirculation line has two recirculation lines, but not anexhaust-gas recirculation arrangement according to the disclosure.

Embodiments of the internal combustion engine are desired in which thecoolers form an integral structural unit. A prefabricated assembly whichcomprises the coolers and which constitutes the entire cooling unitsimplifies the installation of the exhaust-gas recirculation arrangementand of the internal combustion engine as a whole, and thus also reducescosts.

Embodiments of the internal combustion engine may also be desired inwhich the coolers are in the form of individual, separate coolers. Inaccordance with a modular principle, it is then possible usingindividual coolers to form different exhaust-gas recirculationarrangements or to equip different internal combustion engines.

Further alternative embodiments of the internal combustion engineaccording to the disclosure will be discussed herein.

Embodiments of the supercharged internal combustion engine may bedesired may include one or more of a first recirculation line providedin which a first cooler is arranged and which, using at least onecontrol element, is at least connectable upstream of the first cooler tothe exhaust-gas discharge system and downstream of the first cooler tothe intake system, a second recirculation line provided in which asecond cooler is arranged and which, using at least one control element,is at least connectable upstream of the second cooler to the exhaust-gasdischarge system and downstream of the second cooler selectively to theintake system or to the exhaust-gas discharge system, and each coolerhas, for the purposes of energy recovery, at least onecoolant-conducting coolant jacket which serves for the transfer of heatbetween the exhaust gas and the coolant.

It may be desired that no exhaust gas is recirculated after a cold startof the internal combustion engine, because, upon the introduction of therecirculated exhaust gas into the still-cold intake system, aparticularly large amount of condensate may form. With the thendeactivated exhaust-gas recirculation arrangement, it is the case in theprevious examples that the exhaust-gas energy of the hot exhaust gascannot be utilized, despite the fact that a demand for warming theengine oil and the internal combustion engine in targeted fashion existsspecifically after a cold start of the internal combustion engine.

By contrast to this, in the case of the present embodiment, theexhaust-gas energy of the hot exhaust gas can be utilized even when theexhaust-gas recirculation arrangement has been deactivated; at least bymeans of the second cooler which is selectively connectable, downstream,to the intake system or to the exhaust-gas discharge system, with atleast one control element serving for this purpose by means of which theexhaust-gas-conducting lines can be correspondingly switched,specifically connected to the exhaust-gas discharge system. It is thuspossible even when the exhaust-gas recirculation arrangement has beendeactivated for heat to be transferred from the exhaust gas to thecoolant of the second cooler, wherein the coolant flowing or circulatingthrough the second cooler discharges the heat from the interior of thesecond cooler and supplies it for a predefinable use, whereby theefficiency of the internal combustion engine is increased.

Embodiments of the supercharged internal combustion engine may includein which the first recirculation line is, downstream of the firstcooler, at least connectable selectively to the intake system or to theexhaust-gas discharge system using at least one control element.

In the above embodiment, when the exhaust-gas recirculation arrangementhas been deactivated, the exhaust-gas energy of the hot exhaust gas canbe also be utilized by means of the first cooler, which in the presentcase is likewise selectively connectable, downstream, to the intakesystem or to the exhaust-gas discharge system, with at least one controlelement serving for this purpose by means of which theexhaust-gas-conducting lines can be correspondingly switched,specifically connected to the exhaust-gas discharge system.

Thus, when the exhaust-gas recirculation arrangement has beendeactivated, it is possible for both coolers of the exhaust-gasrecirculation arrangement to be utilized for energy recovery and forimproving the efficiency of the internal combustion engine.

It is also possible for the first and/or second cooler to be permanentlyconnected, upstream, to the exhaust-gas discharge system, wherein atleast one control element provided downstream of the cooler is adjustedor switched such that the cooler is connected, downstream, to the intakesystem or to the exhaust-gas discharge system.

Embodiments of the supercharged internal combustion engine may furtherinclude in which the first recirculation line branches off from theexhaust-gas discharge system so as to form a first junction point andopens into the intake system so as to form a second junction point.

In this context, embodiments of the supercharged internal combustionengine may further include in which a first control element is providedin the first recirculation line at the second junction point.

The first control element functions as an EGR valve and, when theexhaust-gas recirculation arrangement is active, serves for theadjustment of the recirculation rate, or at least of the exhaust-gasflow rate recirculated via the first recirculation line. The use of acombination valve arranged at the second junction point permitsdimensioning of the recirculated exhaust-gas flow rate and at the sametime throttling of the intake fresh-air flow rate.

A combination valve of said type may for example be a flap which ispivotable about an axis running transversely with respect to thefresh-air flow, in such a way that, in a first end position, the frontside of the flap blocks the intake system, and at the same time therecirculation line is opened up, and, in a second end position, the backside of the flap covers the recirculation line, and at the same time theintake system is opened up. An additional valve body which is connectedand thereby mechanically coupled to the flap either opens up or blocksthe recirculation line. Whereas the flap serves for the adjustment ofthe air flow rate supplied via the intake system, the valve body effectsthe metering of the recirculated exhaust-gas flow rate.

Embodiments of the supercharged internal combustion engine may furtherinclude in which the second recirculation line branches off from theexhaust-gas discharge system so as to form a third junction point andopens into the intake system so as to form a fourth junction point.

However, in the above-described context, in particular, embodiments ofthe supercharged internal combustion engine may further include in whichthe second recirculation line branches off from the exhaust-gasdischarge system so as to form a third junction point and opens into thefirst recirculation line downstream of the first cooler so as to form afourth junction point.

Then, when the exhaust-gas recirculation arrangement is active, acontrol element provided at the second junction point can serve foradjusting the entire recirculation rate, specifically both theexhaust-gas flow rate recirculated by the first recirculation line andthe exhaust-gas flow rate recirculated by the second recirculation line.

Here, embodiments of the supercharged internal combustion engine mayfurther include in which a second control element is provided in thesecond recirculation line downstream of the second cooler. Said secondcontrol element may be used for activating and deactivating the secondcooler.

The second control element may however in some cases also be utilizedfor connecting the second cooler, downstream, to the exhaust-gasdischarge system, for which purpose further exhaust-gas-conducting linesmay be provided if desired. The second cooler then does not cool anyexhaust gas for recirculation. Rather, the second cooler cools exhaustgas which has been extracted from the exhaust-gas discharge system andwhich is introduced into the exhaust-gas discharge system again. That isto say, in the present case, the second cooler serves only for energyrecovery, that is to say for making the energy inherent in the exhaustgas utilizable.

For the reasons stated above, embodiments of the supercharged internalcombustion engine may further include in which an exhaust-gas-conductingline is provided which branches off from the second recirculation linedownstream of the second cooler so as to form a fifth junction point andopens into the exhaust-gas discharge system so as to form a sixthjunction point.

Here, embodiments of the supercharged internal combustion engine mayfurther include in which the second control element is arranged at thefifth junction point.

In embodiments in which the second recirculation line opens into thefirst recirculation line downstream of the first cooler so as to form afourth junction point, it is then also possible for the first cooler tobe connected, downstream, to the exhaust-gas discharge system via thefurther exhaust-gas-conducting line. Then, the first cooler does notcool any exhaust gas for recirculation, but rather cools exhaust gasthat is introduced into the exhaust-gas discharge system again. Then,both coolers serve for energy recovery when the exhaust-gasrecirculation arrangement has been deactivated.

In embodiments in which an exhaust-gas-conducting line branches off fromthe second recirculation line downstream of the second cooler and opensinto the exhaust-gas discharge system so as to form a sixth junctionpoint, it may be desired for the sixth junction point to be arranged inthe exhaust-gas discharge system downstream of the first and thirdjunction points.

In this context, embodiments of the supercharged internal combustionengine may further include in which a throttle element is arranged inthe exhaust-gas discharge system upstream of the sixth junction pointand downstream of the first and third junction points. The throttleelement serves for increasing the exhaust-gas pressure upstream in theexhaust-gas discharge system, whereby the driving pressure gradientsacross the cooler are likewise increased and a path for the exhaust gasto circumvent the cooler is eliminated, or the bypassing of the cooleris impeded.

To generate the desired pressure gradient, it is additionally possiblefor a shut-off element to be provided upstream of the point at which theexhaust-gas recirculation arrangement opens into the intake system, inorder, at the inlet side, to reduce the pressure upstream of thecompressor.

Embodiments of the supercharged internal combustion engine may furtherinclude in which at least one compressor which can be driven by means ofan auxiliary drive is arranged in the intake system.

A compressor that can be driven by means of an auxiliary drive, that isto say a supercharger, in relation to an exhaust-gas turbochargerconsists in that the supercharger can generate, and may make available,the demanded charge pressure through a plurality of conditions,specifically regardless of the operating state of the internalcombustion engine. This applies in particular to a supercharger whichcan be driven electrically by means of an electric machine, and istherefore independent of the rotational speed of the crankshaft.

In the previous examples, it is specifically the case that difficultiesare encountered in achieving an increase in power in all engine speedranges by means of exhaust-gas turbocharging. A relatively severe torquedrop is observed in the event of a certain engine speed being undershot.Said torque drop is understandable if one takes into consideration thatthe charge pressure ratio is dependent on the turbine pressure ratio orthe turbine power. If the engine speed is reduced, this leads to asmaller exhaust-gas mass flow and therefore to a lower turbine pressureratio or a lower turbine power. Consequently, toward lower enginespeeds, the charge pressure ratio likewise decreases. This equates to atorque drop.

Embodiments of the supercharged internal combustion engine maynevertheless may further include in which at least one exhaust-gasturbocharger is provided, which comprises a turbine arranged in theexhaust-gas discharge system and a compressor arranged in the intakesystem. In an exhaust-gas turbocharger, a compressor and a turbine arearranged on the same shaft. The hot exhaust-gas flow is fed to theturbine and expands in the turbine with a release of energy, as a resultof which the shaft is set in rotation. The energy supplied by theexhaust-gas flow to the shaft is used for driving the compressor whichis likewise arranged on the shaft. The compressor conveys and compressesthe charge air fed to it, as a result of which supercharging of thecylinders is obtained. A charge-air cooler is advantageously provided inthe intake system downstream of the compressor, by means of whichcharge-air cooler the compressed charge air is cooled before it entersthe at least one cylinder. The cooler lowers the temperature and therebyincreases the density of the charge air, such that the cooler alsocontributes to improved charging of the cylinders, that is to say to agreater air mass. In effect, compression by cooling is obtained.

An exhaust-gas turbocharger in relation to a supercharger—which can bedriven by means of an auxiliary drive—consists in that an exhaust-gasturbocharger utilizes the exhaust-gas energy of the hot exhaust gases,whereas a supercharger draws the energy needed for driving it directlyor indirectly from the internal combustion engine and thus adverselyaffects, that is to say reduces, the efficiency, at least for as long asthe drive energy does not originate from an energy recovery source.

If the supercharger is not one that can be driven by means of anelectric machine, that is to say electrically, a mechanical or kinematicconnection for power transmission is generally needed between thesupercharger and the internal combustion engine, which also adverselyaffects or determines the packaging in the engine bay.

To be able to counteract a torque drop at low engine speeds, embodimentsof the internal combustion engine are particularly advantageous in whichat least two exhaust-gas turbochargers are provided. Specifically, ifthe engine speed is reduced, this leads to a smaller exhaust-gas massflow and therefore to a lower charge-pressure ratio.

Through the use of multiple exhaust-gas turbochargers, for examplemultiple exhaust-gas turbochargers connected in series or parallel, thetorque characteristic of a supercharged internal combustion engine canbe noticeably improved.

In order to improve the torque characteristic, it is possible, inaddition to the at least one exhaust-gas turbocharger, for a furthercompressor to also be provided, specifically either a supercharger thatcan be driven by means of an auxiliary drive or a compressor of afurther exhaust-gas turbocharger.

In this context, embodiments of the supercharged internal combustionengine may further include in which the recirculation lines open intothe intake system downstream of the compressor.

In the case of a so-called high-pressure EGR arrangement, the exhaustgas is introduced into the intake system downstream of the compressor.Here, to provide or ensure the pressure gradient, needed for arecirculation, between the exhaust-gas discharge system and the intakesystem, in the case of an exhaust-gas turbocharging arrangement theexhaust gas is preferably, and commonly, extracted from the exhaust-gasdischarge system upstream of the associated turbine. High-pressure EGRmay not pass the compressor, and therefore does not have to be subjectedto exhaust-gas aftertreatment, for example in a particle filter, beforethe recirculation. There is no risk of deposits in the compressor whichchange the geometry of the compressor, in particular the flow crosssections, and thereby impair the efficiency of the compressor.Condensate formation occurs—if at all—downstream of the compressor,which also, during the course of the compression, heats the charge airthat is supplied to it, and thereby prevents or counteracts condensateformation.

Embodiments of the supercharged internal combustion engine may furtherinclude in which the recirculation lines open into the intake systemupstream of the compressor.

During the operation of an internal combustion engine with exhaust-gasturbocharging and the simultaneous use of a high-pressure EGRarrangement, a conflict may arise when the recirculated exhaust gas isextracted from the exhaust-gas discharge system upstream of the turbineand is no longer available for driving the turbine.

In the event of an increase in the exhaust-gas recirculation rate, theexhaust-gas flow introduced into the turbine simultaneously decreases.The reduced exhaust-gas mass flow through the turbine leads to a lowerturbine pressure ratio, as a result of which the charge pressure ratioalso falls, which equates to a smaller compressor mass flow. Aside fromthe decreasing charge pressure, problems may additionally arise in theoperation of the compressor with regard to the surge limit. Pollutantemissions may increase, for example with regard to the formation of sootduring an acceleration in the case of diesel engines.

For this reason, adequately high charge pressures with simultaneouslyhigh exhaust-gas recirculation rates are desired. One approach to asolution is so-called low-pressure EGR, by means of which exhaust gasthat has already flowed through the turbine is recirculated into theintake system. For this purpose, the low-pressure EGR arrangementextracts exhaust gas from the exhaust-gas discharge system downstream ofthe turbine and conducts said exhaust gas into the intake systempreferably upstream of the compressor, in order to be able to realizethe pressure gradient, desired for a recirculation, between theexhaust-gas discharge system and the intake system.

The exhaust gas which is recirculated via the low-pressure EGRarrangement is mixed with fresh air upstream of the compressor. Themixture of fresh air and recirculated exhaust gas produced in this wayforms the charge air which is supplied to the compressor and compressed,wherein the compressed charge air is cooled, downstream of thecompressor, in a charge-air cooler.

Since exhaust gas is conducted through the compressor, the exhaust gasis preferably subjected to exhaust-gas aftertreatment downstream of theturbine. The low-pressure EGR arrangement may also be combined with ahigh-pressure EGR arrangement. In one example, the exhaust-gasaftertreatment may include a particulate filter so that particulates inthe low-pressure EGR do not impinge onto surfaces of the compressor.

For the reasons already stated, embodiments of the supercharged internalcombustion engine may further include in which the recirculation linesbranch off from the exhaust-gas discharge system upstream of theturbine.

Embodiments of the supercharged internal combustion engine may furtherinclude in which the turbine of an exhaust-gas turbocharger that isprovided has a variable turbine geometry, which permits an extensiveadaptation to the operation of the internal combustion engine throughadjustment of the turbine geometry or of the effective turbine crosssection. Here, adjustable guide blades for influencing the flowdirection are arranged in the inlet region of the turbine. By contrastto the impeller blades of the rotating impeller, the guide blades do notrotate with the shaft of the turbine.

If the turbine has a fixed, invariable geometry, the guide blades arearranged in the inlet region so as to be not only stationary but ratheralso completely immovable, that is to say rigidly fixed, if a guidedevice is provided at all. By contrast, in the case of a variablegeometry, the guide blades are duly arranged so as to be stationary butnot so as to be completely immovable, rather so as to be rotatable abouttheir axis, such that the flow approaching the impeller blades can beinfluenced.

Through adjustment of the turbine geometry, it is possible for theexhaust-gas pressure upstream of the turbine to be influenced, and thusfor the pressure gradient between the exhaust-gas discharge system andintake system, and thus the recirculation rate of the high-pressure EGRarrangement, to be influenced.

For reasons already stated, embodiments of the supercharged internalcombustion engine may further include in which the recirculation linesbranch off from the exhaust-gas discharge system downstream of theturbine.

In this context, embodiments of the supercharged internal combustionengine may further include in which at least one exhaust-gasaftertreatment system is provided in the exhaust-gas discharge systembetween the turbine and the branching-off recirculation lines. Sinceexhaust gas is conducted through the compressor, the exhaust gas may besubjected to exhaust-gas aftertreatment downstream of the turbine.

Here, embodiments of the supercharged internal combustion engine areadvantageous in which a particle filter is provided as exhaust-gasaftertreatment system for the aftertreatment of the exhaust gas.

To minimize the soot emissions, use is in this case made of aregenerative particle filter which filters the soot particles out of theexhaust gas and stores them, with said soot particles being burned offintermittently during the course of the regeneration of the filter. Theregeneration temperatures of the particle filter are approximately 550°C. in the absence of catalytic assistance. Therefore, additionalmeasures are generally implemented in order to ensure a regeneration ofthe filter under all operating conditions.

The regeneration of the filter introduces heat into the exhaust gas andincreases the exhaust-gas temperature and thus the exhaust-gas enthalpy.A more energy-rich exhaust gas is thus available at the outlet of thefilter, which exhaust gas can be utilized in the manner according to thedisclosure.

Embodiments of the supercharged internal combustion engine may furtherinclude in which an oxidation catalytic converter is provided asexhaust-gas aftertreatment system for the aftertreatment of the exhaustgas.

Even without additional measures, oxidation of the unburned hydrocarbonsand of carbon monoxide duly takes place in the exhaust-gas dischargesystem at a sufficiently high temperature level and in the presence ofsufficiently large oxygen quantities. However, on account of theexhaust-gas temperature which falls quickly in the downstream direction,and the consequently rapidly decreasing rate of reaction, said reactionsare quickly halted. Therefore, use is made of catalytic reactors which,using catalytic materials, ensure an oxidation even at low temperatures.If nitrogen oxides are additionally to be reduced, this may, in the caseof the Otto-cycle engine, be achieved through the use of a three-waycatalytic converter.

The oxidation is an exothermic reaction, wherein the heat that isreleased increases the temperature and thus the enthalpy of the exhaustgas. A more energy-rich exhaust gas is thus available at the outlet ofthe oxidation catalytic converter. In this respect, the provision of anoxidation catalytic converter may utilize of the exhaust-gas energyaccording to the disclosure.

Embodiments of the supercharged internal combustion engine may furtherinclude in which a bypass line for circumventing the cooler is provided,which bypass line bypasses the EGR cooler and by means of which bypassline the exhaust gas that is recirculated via the exhaust-gasrecirculation arrangement can be introduced, circumventing the cooler,into the intake system.

It may be expedient to bypass the EGR cooling arrangement for example inorder to prevent heat from additionally being introduced into theliquid-type cooling arrangement of the internal combustion engine. Suchan approach is expedient if the liquid-type cooling arrangement of theinternal combustion engine is already highly loaded, for example infull-load situations. If the exhaust-gas recirculation arrangement isutilized during the course of engine braking, it is likewise expedientfor the hot exhaust gas to be recirculated without being cooled.

Embodiments of the supercharged internal combustion engine may furtherinclude in which a liquid-type cooling arrangement is provided forforming an engine cooling arrangement.

Here, embodiments of the supercharged internal combustion engine mayfurther include in which the at least one cylinder head of the internalcombustion engine is provided with at least one coolant jacket, which isintegrated in the cylinder head, in order to form a liquid-type coolingarrangement.

A liquid-type cooling arrangement may decrease the thermal loading ofsupercharged engines more than that of conventional internal combustionengines. If the cylinder head has an integrated exhaust manifold, saidcylinder head is thermally more highly loaded than a conventionalcylinder head which is equipped with an external manifold. Increaseddemands may be placed on the cooling arrangement.

In this context, embodiments of the supercharged internal combustionengine may further include in which the liquid-type cooling arrangementhas a cooling circuit which comprises the coolers of the exhaust-gasrecirculation arrangement.

If the EGR coolers are incorporated into the cooling circuit of theengine cooling arrangement, numerous components and assemblies needed toform a circuit basically need to be provided only singularly, as thesemay be used both for the cooling circuit of the EGR cooler and also forthat of the engine cooling arrangement, which leads to synergies andcost savings, but also entails a weight saving.

For example, only one pump for conveying the coolant, and one containerfor storing the coolant may be provided. The heat dissipated to thecoolant from the internal combustion engine and from the EGR coolingarrangement can be extracted from the coolant in a common heat exchanger(e.g., a radiator different than the EGR cooling arrangement).

The exhaust-gas energy or exhaust-gas heat that is absorbed by thecoolant in the EGR cooling arrangement can thus likewise be utilizedmore easily, for example for warming the internal combustion engine orthe engine oil.

It should be understood that the summary above is provided to introducein simplified form a selection of concepts that are further described inthe detailed description. It is not meant to identify key or essentialfeatures of the claimed subject matter, the scope of which is defineduniquely by the claims that follow the detailed description.Furthermore, the claimed subject matter is not limited toimplementations that solve any disadvantages noted above or in any partof this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically shows a first embodiment of the superchargedinternal combustion engine together with exhaust-gas recirculationarrangement.

FIG. 2 schematically shows the first embodiment of the superchargedinternal combustion engine together with exhaust-gas recirculationarrangement in a first operating mode.

FIG. 3 schematically shows the first embodiment of the superchargedinternal combustion engine together with exhaust-gas recirculationarrangement in a second operating mode.

FIG. 4 schematically shows the first embodiment of the superchargedinternal combustion engine together with exhaust-gas recirculationarrangement in a third operating mode.

FIG. 5 schematically shows the first embodiment of the superchargedinternal combustion engine together with exhaust-gas recirculationarrangement in a fourth operating mode.

FIG. 6 shows a method for selecting which of the operating modes inwhich to operate the exhaust-gas recirculation arrangement.

DETAILED DESCRIPTION

The following description relates to systems and methods for a coolingarrangement arranged configured to cool EGR and perform energy recovery.The cooling arrangement may be arranged in an exhaust system of anengine, as shown in FIG. 1. The cooling arrangement may comprise two ormore coolers arranged in a shared housing of the arrangement, each ofthe coolers having an inlet and an outlet independent of the othercooler. One or more valves may be located upstream and downstream of thecooling arrangement as shown in FIG. 1.

FIGS. 2, 3, 4, and 5 show exhaust gas flow through the engine system inresponse to actuation of one or more of the valves associated with thecooling arrangement. A method for selecting which of the modesassociated with FIGS. 2-5 to operate the cooling system in based onengine operating conditions is shown in FIG. 6.

Turning now to FIG. 1, it schematically shows a first embodiment of thesupercharged internal combustion engine 1 together with exhaust-gasrecirculation arrangement 4.

The internal combustion engine 1 has an intake system 3 for supplyingcharge air to the cylinders and has an exhaust-gas discharge system 2for discharging the exhaust gases from the cylinders.

For the purposes of supercharging, the internal combustion engine 1 isequipped with an exhaust-gas turbocharger 6 which comprises a turbine 6b arranged in the exhaust-gas discharge system 2 and a compressor 6 aarranged in the intake system 3.

Furthermore, an exhaust-gas recirculation (EGR) arrangement 4 isprovided which has two recirculation lines 4 a, 4 b, wherein coolers 5a, 5 b are arranged in each recirculation line 4 a, 4 b, respectively.The coolers 5 a, 5 b have in each case one coolant-conducting coolantjacket which serves for the transfer of heat between the exhaust gas andthe coolant. The coolers 5 a, 5 b are arranged in parallel and aremutually independently usable for the cooling of exhaust gas or forenergy recovery and fluidly connected or connectable to the enginecooling arrangement. As such, herein, the EGR arrangement 4 may beinterchangeably referred to as the cooling arrangement 4. Specifically,a coolant system 20 is shown fluidly coupled to each of the coolers 5 a,5 b. Additionally, the coolant system 20 is shown coupled to the engine1 a. It will be appreciated that in some embodiments, the coolant system20 is separated from a coolant system of the engine 1 a withoutdeparting from the scope of the present disclosure.

The first recirculation line 4 a branches off from the exhaust-gasdischarge system 2 downstream of the turbine 6 b so as to form a firstjunction point 2 a, and opens into the intake system 3 upstream of thecompressor 6 a so as to form a second junction point 3 a. A firstcontrol element 7 is provided at the second junction point 3 a. Acombination valve 7 a is used as first control element 7, whichcombination valve serves for the adjustment of the recirculatedexhaust-gas flow rate, that is to say of the recirculation rate, andthus also for at least partial deactivation of the cooling arrangement4.

The second recirculation line 4 b likewise branches off from theexhaust-gas discharge system 2 downstream of the turbine 6 b anddownstream of the first junction point 2 a so as to form a thirdjunction point 2 c and opens into the first recirculation line 4 adownstream of the first cooler 5 a so as to form a fourth junction point10.

A further exhaust-gas-conducting line 11 is provided which branches offfrom the second recirculation line 4 b downstream of the second cooler 5b so as to form a fifth junction point 12 and opens into the exhaust-gasdischarge system 2 so as to form a sixth junction point 2 d.

In the present case, the sixth junction point 2 d is arranged in theexhaust-gas discharge system 2 downstream of the first and thirdjunction points 2 a, 2 c, respectively. A throttle element 2 b isarranged in the exhaust-gas discharge system 2 upstream of the sixthjunction point 2 d and downstream of the first and third junction points2 a, 2 c. The throttle element 2 b serves for increasing the exhaust-gaspressure upstream in the exhaust-gas discharge system 2, whereby thedriving pressure gradients across the coolers 5 a, 5 b likewiseincrease.

A second control element 8 is provided in the second recirculation line4 b downstream of the second cooler 5 b, which second control element isarranged at the fifth junction point 12. The second control element 8 isa 3/3-way valve 8 a which has three line connectors and three switchingpositions and which connects the two coolers 5 a, 5 b via the secondjunction point 3 a to the intake system 3 or via the sixth junctionpoint 2 d to the exhaust-gas discharge system 2, or else deactivates thesecond cooler 5 b, that is to say separates said second cooler from thefirst recirculation line 4 a and connects said second cooler to theexhaust-gas discharge system 2 via the sixth junction point 2 d.

Both coolers 5 a, 5 b can thus be used for cooling EGR but also forenergy recovery when one or more of EGR cooling is not desired and acurrent EGR cooling is not sufficient to meet a current energy recoverydemand. This will be discussed in more detail below on the basis ofFIGS. 2 to 5.

The supercharged internal combustion engine 1 may further includecontrol system 14. Control system 14 is shown receiving information froma plurality of sensors 16 (various examples of which are describedherein) and sending control signals to a plurality of actuators 81(various examples of which are described herein). As one example,sensors 16 may include exhaust flow rate sensor configured to measure aflow rate of exhaust gas through the exhaust system 2, exhaust gassensor (located in an exhaust manifold of exhaust system 2), atemperature sensor, a pressure sensor (optionally located downstream ofexhaust-gas aftertreatment system 9), and PM sensor. Other sensors suchas additional pressure, temperature, air/fuel ratio, exhaust flow rateand composition sensors may be coupled to various locations in thesupercharged internal combustion engine 1. As another example, theactuators may include fuel injectors, throttle, DPF valves that controlfilter regeneration, switch of electric circuit, etc. The control system14 may include a controller 13. The controller 13 may be configured withcomputer readable instructions stored on non-transitory memory. Thecontroller 13 receives signals from the various sensors of FIG. 1,processes the signals, and employs the various actuators of FIG. 1 toadjust engine operation based on the received signals and instructionsstored on a memory of the controller.

FIG. 2 schematically shows the first embodiment of the superchargedinternal combustion engine 1 together with exhaust-gas recirculationarrangement 4 in a first operating mode. It is sought merely to explainthe additional features in relation to FIG. 1, for which reasonreference is made otherwise to FIG. 1. Thus, components previouslyintroduced may be similarly numbered in subsequent figures.

In the description herein, EGR refers to exhaust gas for recirculation.As such, EGR flows from one or more of the coolers 5 a, 5 b to theintake system 3. Alternatively, exhaust gas for energy recovery does notflow to the intake system 3. The exhaust gas is returned to the exhaustsystem 2 from one or more of the cooler 5 a, 5 b.

In the first operating mode, both coolers 5 a, 5 b may cool EGR. In theembodiment of FIG. 2, both coolers are shown cooling EGR. The secondrecirculation line 4 b is connected to the first recirculation line 4 a,and the first recirculation line 4 a is connected to the intake system3. The first and second control elements 7, 8 are switched or setcorrespondingly.

Said another way, in the first mode, cooled EGR is desired by the engine1 a. In the current example, an EGR flow rate desired may be greaterthan a capacity of a single cooler (e.g., cooler 5 a or cooler 5 b). Assuch, EGR flows to both the coolers 5 a, 5 b. The control element 7 amay be adjusted to a position such that gas in the first recirculationline 4 a may flow through the second junction 3 a and into the intakesystem. The control element 8 a may be adjusted to a position such thatcooler EGR from the cooler 5 b flows through the second recirculationline 4 b, through the fifth junction 12, through the fourth junction 10,and into the first recirculation line 4 a. Thus, cooled EGR from thecooler 5 b may mix and/or merge with cooler EGR from the cooler 5 a inthe first recirculation line 4 a. Herein, the cooler 5 a may be referredto as first cooler 5 a and the cooler 5 b may be referred to as secondcooler 5 b.

FIG. 3 schematically shows the first embodiment of the superchargedinternal combustion engine 1 together with exhaust-gas recirculationarrangement 4 in a second operating mode. It is sought merely to explainthe additional features in relation to FIG. 1, for which reasonreference is made otherwise to FIG. 1.

In the second operating mode, only the first cooler 5 a may cool EGR,for which purpose the first recirculation line 4 a is connected to theintake system 3 via the second junction point 3 a. The secondrecirculation line 4 b together with the second cooler 5 b is separatedfrom the first recirculation line 4 a and is connected to theexhaust-gas discharge system 2 via the sixth junction point 2 d. Thesecond cooler 5 b thus serves for energy recovery. The first and secondcontrol elements 7, 8 are switched or set correspondingly.

Said another way, in the second operating mode, the first cooler 5 a maybe configured to cool EGR and the second cooler 5 b may be configured tocool exhaust gas for heat recovery. As such, the second control element8 may be switched to a position fluidly sealing the second recirculationline 4 b from the first recirculation line 4 a. As such, gases from thefirst cooler 5 a and the second cooler 5 b may not mix during the secondmode.

EGR from the first cooler 5 a flows through the fourth junction 10,through the first recirculation line 4 a, through the second junction 3a, and into the intake system 3. Thus, the first control element 7 is ina position configured to allow gases from the first recirculation line 4a to flow into the intake system 3.

Exhaust gas for heat recovery from the second cooler 5 b flows throughthe fifth junction 12, through the exhaust-gas-conducting-line 11, andinto the sixth junction point 2 d of the exhaust system 2. Thus, thesecond control element 8 may be in a position configured to allow gasesfrom the second recirculation line to flow back to the exhaust system 2.Additionally, in one example, the second mode does not allow gases fromthe first cooler 5 a to mix with gases from the second cooler 5 b. Inthis way, the second mode provides cooled EGR to the intake system viathe first cooler 5 a, and energy recovery via at least the second cooler5 b. It will be appreciated that coolant from the first cooler 5 a,which has cooled EGR, may also be used for energy recovery purposes. Assuch, the first cooler 5 a and the second cooler 5 b may be used to meetan energy recovery demand during the second mode.

FIG. 4 schematically shows the first embodiment of the superchargedinternal combustion engine 1 together with exhaust-gas recirculationarrangement 4 in a third operating mode. It is sought merely to explainthe additional features in relation to FIG. 1, for which reasonreference is made otherwise to FIG. 1.

In the third operating mode, cooled EGR is not desired, and both coolers5 a, 5 b of the cooling arrangement 4 are used for energy recovery. Thefirst and second control elements 7, 8 are switched or setcorrespondingly. Both coolers 5 a, 5 b are connected to the exhaust-gasdischarge system 2 via the sixth junction point 2 d and separated fromthe intake system 3.

Said another way, the third mode corresponds to conditions where theengine 1 a does not desire EGR cooling but does desired exhaust gas heatrecovery. In one example, this may occur following a cold-start, whereinthe engine temperature is greater than an ambient temperature, but atransmission temperature is less than a desired temperature and/or acabin heating request is still unmet. As such, EGR cooling may not bedesired, but exhaust gas heat recovery may be desired.

Thus, the cooling arrangement 4 is deactivated with regards to coolingEGR. However, the cooling arrangement 4 is still active in terms ofcooling exhaust gas, specifically, exhaust gas for heat recovery. Assuch, the first control element 7 is moved to a position where gasesfrom the first recirculation line 4 a are prohibited from flowing to theintake system 3. Furthermore, the second control element 8 is adjustedto a position where gases from the first recirculation line 4 a and thesecond recirculation line 4 b may flow into the exhaust-gas-conductingline 11. The exhaust gases from the first cooler 5 a and the secondcooler 5 b may mix in the exhaust-gas-conducting line 11 before flowingto the sixth junction 2 d of the exhaust system 2. It will beappreciated by those of ordinary skill in the art that EGR may flow tothe intake system 3 during the third operating mode, however, the EGR isnot cooled by the cooling arrangement 4.

The embodiment of FIG. 4 shows both the first cooler 5 a and the secondcooler 5 b being used to meet an energy recovery demand. However, itwill be appreciated by those of ordinary skill in the art that only onecooler of the coolers 5 a, 5 b may be used during the third operatingmode if a single cooler may meet the energy recovery demand. As such,either the first cooler 5 a or the second cooler 5 b may be activatedduring the third mode.

For example, if the energy recovery demand is less than or equal to athreshold energy recovery demand, the threshold energy recovery demandcorresponding to a maximum amount of energy recovery a single cooler isconfigured to perform, then the third mode may comprise flowing exhaustgas for heat recovery to only one cooler of the coolers 5 a, 5 b. As anexample, if only the second cooler 5 b is used, then the first controlelement 7 is adjusted to a position to fluidly seal the firstrecirculation line from the intake system 3. Additionally, the secondcontrol element 8 is adjusted to a position to fluidly seal the firstrecirculation line 4 a from the exhaust-gas-conducting line 11.Furthermore, the second control element 8 is adjusted to a position tofluidly couple the second recirculation line 4 b to theexhaust-gas-conducting line 11. Additionally or alternatively, coolantmay only flow to the second cooler 5 b. As such, even if exhaust gasflows to the first cooler 5 a, it does not communicate with any coolantflowing to the cooling arrangement 4.

FIG. 5 schematically shows the first embodiment of the superchargedinternal combustion engine 1 together with exhaust-gas recirculationarrangement 4 in a fourth operating mode. It is sought merely to explainthe additional features in relation to FIG. 1, for which reasonreference is made otherwise to FIG. 1.

Both coolers 5 a, 5 b have been deactivated, both with regard to coolingof exhaust gas for recirculation and with regard to energy recovery. Thecooling arrangement 4 and the energy recovery have been deactivated. Inone example, coolant does not flow to both the first cooler 5 a and thesecond cooler 5 b. The first and second control elements 7, 8 areswitched or set correspondingly.

Said another way, the fourth mode may correspond to conditions of theengine 1 a wherein EGR cooling is not desired and heat recovery is notdesired. As an example, this may occur during a mid-load where cabinheating is not desired and the engine and transmission are operatingwithin desired operating ranges.

In one example, the first recirculation line 4 a is fluidly sealed fromthe intake system 3 and the second recirculation line 4 b is fluidlysealed from the exhaust-gas-conducting line 11 via the first controlelement 7 and second control element 8, respectively. As such, exhaustgas remains in the exhaust system 2 and is not cooled during the fourthmode.

Turning now to FIG. 6, it shows a method for determining which of thefirst, second, third, or fourth modes to operate the cooling arrangement4. Instructions for carrying out method 600 may be executed by acontroller based on instructions stored on a memory of the controllerand in conjunction with signals received from sensors of the enginesystem, such as the sensors described above with reference to FIG. 1.The controller may employ engine actuators of the engine system toadjust engine operation, according to the methods described below.

Method 600 may be described in reference to components previouslydescribed with respect to FIGS. 1-5. Specifically, the method 600 mayinclude the first control element 7, the second control element 8, thefirst recirculation passage 4 a, the second recirculation passage 4 b,the exhaust-gas-conducting line 11, the exhaust system 2, the intakesystem 3, the engine 1 a, and the controller 13.

In one example, the method may include determining first mode conditionsbeing met, and in response thereto performing EGR cooling; anddetermining second mode conditions being met (where the second mode isnot the same as the first mode), and in response thereto performing EGRcooling and exhaust gas energy recovery. Additionally or alternatively,the method may further include determining if third mode conditions aremet, and in response thereto performing exhaust gas energy recoverywithout EGR cooling. If none of the first, second, and third modeconditions are met, then the method may include determining that fourthmode conditions are met, and in response thereto performing neither EGRcooling or exhaust gas heat recovery. As an example, first, second, andthird mode conditions may be determined based on feedback from theengine temperature sensor, a transmission temperature sensor, and theexhaust gas sensor.

The method 600 begins at 602, where the method includes determining,estimating, and/or measuring current engine operating parameters.Current engine operating parameters may include but are not limited toone or more engine temperature, engine load, manifold vacuum, EGR flowrate, exhaust back pressure, transmission temperature, cabin heatingdemand, and air/fuel ratio.

The method 600 may proceed to 604, where the method may includedetermining if first mode conditions. As described above, the firstoperating mode may include flowing only EGR through the coolers of thecooling arrangement. As such, the first mode conditions may include oneor more of an EGR cooling demand being greater than threshold EGRcooling demand and the EGR cooling demand being greater than an energyrecovery demand. The threshold EGR cooling demand may be based on amaximum cooling a single cooler of the coolers of the coolingarrangement is configured to provide. Thus, if the EGR cooling demand isgreater than the threshold EGR cooling demand, then both coolers may beneeded to meet the EGR cooling demand and first mode conditions may bemet. In one example, both the first cooler 5 a and the second cooler 5 breceive EGR, where the EGR from the first and second coolers merge inthe first recirculation line before flowing to the intake system 3.

Additionally or alternatively, if the EGR cooling demand is greater thanthe energy recovery demand, then coolant used to cool the EGR in thecoolers may be sufficient to meet the energy heat recovery demand. Saidanother way, the heat transfer between the EGR and the coolant in one ormore of the coolers of the cooling arrangement may meet the energy heatrecovery demand without flowing exhaust gas for energy recovery.

If the first mode conditions are met and at least some amount of EGRcooling is desired, then the method proceeds to 606 and flows EGR to oneor more of the first and second coolers. As an example, if the EGRcooling demand is less than or equal to the threshold EGR cooling demandand the EGR cooling demand is greater than or equal to the energyrecovery demand, then EGR may flow to only one of the first and secondcoolers. In one example, the EGR flows to only the first cooler 5 a, andthe first control element 7 is adjusted to an open position such thatEGR from the first recirculation line 4 a flows to the intake system.Furthermore, the second control element 8 is moved to a closed positionto fluidly seal the second recirculation line 4 b from the firstrecirculation line 4 a. Additionally, coolant may only flow to the firstcooler 5 a and does not flow to the second cooler 5 b. As such, even ifexhaust gas flows to the second cooler 5 b during the first mode whenonly one cooler is sufficient to meet the EGR cooling demand, theexhaust gas may flow through the second recirculation line 4 b to theexhaust-gas-conducting line 11 and back to the exhaust system 2.

Additionally or alternatively, if the EGR cooling demand is greater thanthe threshold EGR cooling demand, then EGR is directed to both the firstand second coolers. In one example, the first controller element 7 isadjusted to the open position such that EGR from the first recirculationline 4 a flows to the intake system. Furthermore, the second controlelement is moved to an open position to fluidly couple the secondrecirculation line 4 b to the first recirculation line 4 a. As such, EGRfrom the first cooler 5 a and the second cooler 5 b may mix in the firstrecirculation line 4 a before entering the intake system 3.

The method 600 may proceed to 608 and does not flow exhaust gas for onlyheat recovery. As such, any exhaust gas flowing to the coolers duringthe first mode is directed to the intake system during the first mode.As described above, any energy recovery demands may be met during thefirst mode due to the EGR cooling demand being greater than the heatrecovery demand.

Returning to 604, if the first mode conditions are not met, then themethod 600 may proceed to 610 to determine if second mode conditions aremet. In one example, first mode conditions are not met if the EGRcooling demand is less than the energy recovery demand. Second modeconditions thus may include the energy recovery demand being greaterthan the EGR cooling demand and the EGR cooling demand being greaterthan zero. Additionally or alternatively, the EGR cooling demand is lessthan or equal to the threshold EGR cooling demand such that a singlecooler may meet the EGR cooling demand.

If the second mode conditions are met, then the method 600 may proceedto 612 to flow EGR and exhaust gas to the first and second coolers,respectively. EGR from the first cooler flows through the firstrecirculation line to the intake system and exhaust gas from the secondcooler flows through the second recirculation line back to the exhaustsystem. In one example, the first control element is in the openposition configured to allow gas from the first recirculation line toenter the intake system. The second control element is in the closedposition configured to allow gas from the second recirculation line toenter the exhaust-gas-conducting line.

The method 600 may proceed to 614 where gas from the secondrecirculation line, and therefore the second cooler, does not enter thefirst recirculation line or mix with gas from the first cooler.

In one example, if second mode conditions are met and the energyrecovery demand is greater than the threshold energy recovery demand andthe EGR cooling demand is unable to meet the difference between theenergy recovery demand and the threshold energy recovery demand, thenone or more engine operating parameters may be adjusted to meet theenergy recovery demand. For example, exhaust gas temperatures may beincreased by one or more of retarding a spark timing, increasing apost-injection pressure, and the like. This may increase exhaust gastemperatures, thereby allowing the hotter exhaust gas and EGR totransfer more heat to coolant in the coolers to meet the energy recoverydemand.

Returning to 610, if the second mode conditions are not met, then themethod 600 may proceed to 616 to determine if third mode conditions aremet. In one example, second mode conditions are not met if the EGRcooling demand is not present (e.g., zero) and the energy recoverydemand is not present (e.g., zero). Thus, the third mode conditions mayinclude the EGR cooling demand not being present and the energy recoverydemand being greater than zero.

If the third mode conditions are met, the method 600 may proceed to 618to flow exhaust gas to one or more of the first and second coolers basedon the energy recovery demand. For example, if the energy recoverydemand is greater than the threshold energy recovery demand, thenexhaust gas is directed from the exhaust system to each of the first andsecond coolers. The first cooler may flow cooled exhaust gas to thefirst recirculation line, where gas from the first recirculation linemixes with gases from the second cooler in the exhaust-gas-conductingline before flowing back to the exhaust system. Additionally, the firstcontrol element is in a closed position such that gas in the firstrecirculation line may not flow to the intake system.

However, if the energy recovery demand is less than or equal to thethreshold energy recovery demand, then exhaust gas is directed from theexhaust system to one or more first or second coolers. In one example,energy recovery occurs in the second cooler when the energy recoverydemand is less than or equal to the threshold energy recovery demand.The second control element may be moved to a position fluidlydisconnecting the first recirculation line from theexhaust-gas-conducting line such that only gases from the secondrecirculation line may flow to the exhaust-gas-conducting line.Additionally or alternatively, coolant flow to the first cooler may beterminated. In this way, even if the second control element is in aposition where the first recirculation line is fluidly coupled to theexhaust-gas-conducting line, the exhaust gas flowing through the firstcooler does not thermally communicate with coolant. Thus, exhaust gasflowing out of the first cooler is hotter than exhaust gas flowing outof the second cooler when the energy recovery demand is less than orequal to the threshold energy recovery demand.

The method 600 may proceed to 620 where the method may include notflowing cooled EGR to the intake system. In one example the intakesystem may receive EGR during the third mode, however, the EGR does notflow through the cooling arrangement (e.g., cooling arrangement 4 ofFIGS. 1-5). This may be accomplished by adjusting the first controlelement to the closed position to hermetically seal the intake systemfrom the first recirculation line.

Returning to 616, if third mode conditions are not met, then the method600 may proceed to 622 and enter the fourth mode. In one example, thefourth mode is selected when none of the conditions for the first mode,second mode, and third mode are met. In one example, the fourth modeconditions include the EGR cooling demand being zero and the energyrecovery demand being zero.

At 624, the method 600 may include adjusting the throttle element tomitigate and/or prevent exhaust gas from flowing to the first and secondcoolers. Additionally or alternatively, the first control element ismoved to the closed position to fluidly seal the intake system from thefirst recirculation line.

At 626, the method 600 may include not flowing coolant to the coolingarrangement. As such, the fourth mode may not cool EGR or perform heatrecovery.

Along with instructions for implementing the method 600, the controllermay further include instructions for transitioning between the first,second, third, and fourth modes based on feedback from one or more ofthe sensors described above. As an example of a transition from thefirst mode to the second mode, the transition may occur in response tothe energy recovery demand being greater than the EGR cooling demand andthe EGR cooling demand being less than the threshold EGR cooling demand.During the transition, the second control element may be adjusted tofluidly seal the second recirculation line from the first recirculationline. However, the first control element may maintain the position heldduring the first mode. A position of the throttle element in the exhaustsystem may also remain in a similar position as that held during thefirst mode.

In this way, a heat exchanger system comprises two coolers arranged in asingle housing. The coolers may be fluidly coupled to a shared coolingsystem such that thermal transfers between exhaust gas and coolant ineach of the coolers may be used for energy recovery purposes. Thetechnical effect of having two coolers arranged in a shared housing isto allow the heat exchanger system to perform energy recovery duringconditions where EGR cooling may not be desired. This may allow thesystem to reduce cold-start times while providing a heat exchangersystem that reduces packaging constraints and reduces manufacturingcosts.

A method comprises flowing only exhaust-gas recirculate to a coolingarrangement during a first mode, flowing exhaust-gas recirculate andexhaust gas to the cooling arrangement during a second mode, and flowingonly exhaust gas to the cooling arrangement during a third mode, wherethe cooling arrangement comprises a single housing having two fluidlyseparate coolers. A first example of the method further includes wherethe first mode occurs in response to an EGR cooling demand being greaterthan or equal to an energy recovery demand, and where the second modeoccurs in response to one or more of the EGR cooling demand being lessthan the energy recovery demand and the EGR cooling demand being lessthan a threshold EGR cooling demand, and where the third mode occurs inresponse to the EGR cooling demand being zero and the energy recoverydemand being greater than zero. A second example of the method,optionally including the first example, further includes where thethreshold cooling demand is based on a maximum cooling ability of asingle cooler of the coolers. A third example of the method, optionallyincluding the first and/or second examples, further includes where afourth mode, where the fourth mode includes not flowing coolant to thecoolers of the cooling arrangement, wherein the coolant flows from acoolant system coupled to an engine. A fourth example of the method,optionally including one or more of the first through third examples,further includes where the coolers include a first cooler adjacent to asecond cooler in the single housing, the first cooler being fluidlycoupled to an exhaust system upstream of a throttle element and to anintake system upstream of a compressor via a first recirculation line,and where the first recirculation line is selectively fluidly coupled tothe intake system via a first control element, and where the secondcooler is fluidly coupled to the exhaust system at a location upstreamof the throttle element and downstream of the first recirculation linevia a second recirculation line, and where the second recirculation lineis selectively fluidly coupled to the first recirculation line via asecond control element. A fifth example of the method, optionallyincluding one or more of the first through fourth examples, furtherinclude where the second control element is further configured toselectively couple the second recirculation line to anexhaust-gas-conducting line, the exhaust-gas-conducting line fluidlycoupled to a portion of the exhaust system downstream of the throttleelement.

A system comprises a cooling arrangement having a single housingcomprising a first cooler adjacent to and fluidly separated from asecond cooler, a single coolant system configured to flow coolant to thefirst and second coolers separately, and a controller withcomputer-readable instructions stored on non-transitory memory thereofthat when executed enable the controller to flow only exhaust-gasrecirculate to one or more of the first and second coolers in responseto an exhaust-gas recirculate cooling demand being greater than anenergy recovery demand, flow exhaust-gas recirculate and exhaust gas tothe first and second coolers, respectively, in response to the energyrecovery demand being greater than the exhaust-gas recirculate coolingdemand, the exhaust-gas recirculate cooling demand being greater thanzero, and flow only exhaust gas to one or more of the first and secondcoolers in response to the exhaust-gas recirculate cooling demand beingzero and the energy recovery demand being greater than zero. A firstexample of the system further includes where the first cooler isarranged along a first recirculation line, and where the firstrecirculation line is fluidly coupled to an exhaust system at a firstjunction and to an intake system at a second junction, the secondjunction further comprising a first control element configured toselectively fluidly couple the first recirculation line to the intakesystem, where the first junction is upstream of the first cooler and thesecond junction is downstream of the first cooler, and where the secondcooler is arranged along a second recirculation line, and where thesecond recirculation line is fluidly coupled to the exhaust system at athird junction upstream of the second cooler, and where the secondrecirculation line is fluidly coupled to the first recirculation line ata fourth junction downstream of each of the first and second coolers,and where the second recirculation line further comprises a secondcontrol element arranged at a fifth junction, the fifth junctionarranged downstream of the second cooler, and where the second controlelement selectively fluidly couples the second recirculation line to thefirst recirculation line or to an exhaust-gas-conducting line, and wherethe exhaust gas conducting line is fluidly coupled to the exhaust systemat a sixth junction, and where the sixth junction is downstream of eachof the first junction, the third junction, and a throttle element. Asecond example of the system, optionally including the first example,further includes where exhaust-gas recirculate flows through the firstrecirculation line to the intake system and where exhaust gas flowsthrough the exhaust-gas-conducting line to the exhaust system. A thirdexample of the system, optionally including the first and/or secondexamples, further includes where the coolant system is further fluidlycoupled to an engine. A fourth example of the system, optionallyincluding one or more of the first through third examples, furtherincludes where the controller further comprises instructions for notflowing coolant to the first cooler and the second cooler during afourth mode in response to the exhaust-gas recirculate cooling demandbeing zero and the energy recovery demand being zero. A fifth example ofthe system, optionally including one or more of the first through fourthexamples, further includes where the first mode further comprisesflowing exhaust-gas recirculate to only one of the first or secondcoolers in response to the exhaust-gas recirculate cooling demand beingless than or equal to a threshold exhaust-gas recirculate coolingdemand, and where the third mode further comprises flowing exhaust gasto only one of the first or second cooler in response to the energyrecovery demand being less than or equal to a threshold energy recoverydemand, and where the threshold exhaust-gas recirculate cooling demandand the threshold energy recovery demand are based on a maximum coolingability of one of the first and second coolers.

Note that the example control and estimation routines included hereincan be used with various engine and/or vehicle system configurations.The control methods and routines disclosed herein may be stored asexecutable instructions in non-transitory memory and may be carried outby the control system including the controller in combination with thevarious sensors, actuators, and other engine hardware. The specificroutines described herein may represent one or more of any number ofprocessing strategies such as event-driven, interrupt-driven,multi-tasking, multi-threading, and the like. As such, various actions,operations, and/or functions illustrated may be performed in thesequence illustrated, in parallel, or in some cases omitted. Likewise,the order of processing is not necessarily required to achieve thefeatures and advantages of the example embodiments described herein, butis provided for ease of illustration and description. One or more of theillustrated actions, operations and/or functions may be repeatedlyperformed depending on the particular strategy being used. Further, thedescribed actions, operations and/or functions may graphically representcode to be programmed into non-transitory memory of the computerreadable storage medium in the engine control system, where thedescribed actions are carried out by executing the instructions in asystem including the various engine hardware components in combinationwith the electronic controller.

It will be appreciated that the configurations and routines disclosedherein are exemplary in nature, and that these specific embodiments arenot to be considered in a limiting sense, because numerous variationsare possible. For example, the above technology can be applied to V-6,I-4, I-6, V-12, opposed 4, and other engine types. The subject matter ofthe present disclosure includes all novel and non-obvious combinationsand sub-combinations of the various systems and configurations, andother features, functions, and/or properties disclosed herein.

The following claims particularly point out certain combinations andsub-combinations regarded as novel and non-obvious. These claims mayrefer to “an” element or “a first” element or the equivalent thereof.Such claims should be understood to include incorporation of one or moresuch elements, neither requiring nor excluding two or more suchelements. Other combinations and sub-combinations of the disclosedfeatures, functions, elements, and/or properties may be claimed throughamendment of the present claims or through presentation of new claims inthis or a related application. Such claims, whether broader, narrower,equal, or different in scope to the original claims, also are regardedas included within the subject matter of the present disclosure.

The invention claimed is:
 1. A supercharged internal combustion enginecomprising: an intake system for supplying air to the engine, anexhaust-gas discharge system for discharging exhaust gases, and anexhaust-gas recirculation arrangement which comprises at least onerecirculation line, with at least one cooler and at least one controlelement being provided in the at least one recirculation line for thepurposes of setting a predefinable exhaust-gas flow rate forrecirculation, wherein at least two recirculation lines are provided, inwhich there is arranged in each case one cooler, the coolers beingarranged in parallel and being usable independently of one another forcooling exhaust gas for the purposes of energy recovery, wherein a firstrecirculation line is provided comprising at least a first cooler, thefirst recirculation line fluidly coupled to the exhaust-gas dischargesystem upstream of the first cooler, the first recirculation linefurther fluidly coupled to the intake system downstream of the firstcooler, where a first control element is arranged at a junction betweenthe first recirculation line and the intake system; a secondrecirculation line is provided comprising at least a second cooler, thesecond recirculation line fluidly coupled to the exhaust gas dischargesystem upstream of the second cooler, and where the second recirculationline further comprises a second control element selectively fluidlycoupling the second recirculation line to the first recirculation lineor to an exhaust-gas-conducting line configured to return exhaust gas tothe exhaust-gas discharge system, where the second control element isdownstream of the second cooler; and the first and second coolerscomprise at least one coolant-conducting jacket configured to allowcoolant flowing therethrough to thermally communicate with exhaust gas.2. The supercharged internal combustion engine of claim 1, wherein thefirst recirculation line branches off from the exhaust-gas dischargesystem so as to form a first junction point and opens into the intakesystem so as to form a second junction point, the first control elementbeing arranged at the second junction point.
 3. The superchargedinternal combustion engine of claim 2, wherein the second recirculationline branches off from the exhaust-gas discharge system so as to form athird junction point and opens into the first recirculation linedownstream of the first cooler so as to form a fourth junction point. 4.The supercharged internal combustion engine of claim 3, wherein theexhaust-gas-conducting line is provided which branches off from thesecond recirculation line downstream of the second cooler so as to forma fifth junction point and opens into the exhaust-gas discharge systemso as to form a sixth junction point, wherein the second control elementis arranged at the fifth junction point and where the sixth junctionpoint is downstream of the first and third junction points and athrottle element arranged in the exhaust-gas discharge system, thethrottle element being arranged downstream of the first and thirdjunction points.
 5. The supercharged internal combustion engine of claim1, further comprising at least one exhaust-gas turbocharger comprising aturbine arranged in the exhaust-gas discharge system and a compressorarranged in the intake system.
 6. The supercharged internal combustionengine of claim 5, where the exhaust-gas discharge system comprises anaftertreatment device arranged downstream of the turbine, and where theaftertreatment device is a particulate filter.
 7. The superchargedinternal combustion engine of claim 1, further comprising a liquid-typecooling arrangement provided for forming an engine cooling arrangement,and where the engine cooling arrangement is fluidly coupled to each ofthe coolers.
 8. A method comprising: with a controller, performing thefollowing actions: flowing exhaust-gas to a first cooler and a secondcooler of recirculate a cooling arrangement during a first mode via afirst recirculation line comprising the first cooler and a secondrecirculation line comprising the second cooler, wherein the first modefurther comprises actuating a first valve to an open position to fluidlycouple the first recirculation line to an intake system, wherein asecond valve is actuated to fluidly couple the second recirculation lineto the first recirculation line; during a second mode, flowingexhaust-gas from the first cooler to the intake system via the firstvalve in the open position, the second mode further comprising adjustingthe second valve to fluidly couple the second recirculation line to afurther exhaust-gas discharge line, wherein the second valve blocksexhaust gas flow from the second recirculation line to the firstrecirculation line in the second mode, wherein the exhaust-gas dischargeline is configured to flow exhaust gas to an exhaust-gas dischargesystem; and flowing exhaust gas to the first and second coolers during athird mode, wherein the first valve is actuated to block exhaust flowfrom the first recirculation line to the intake system and the secondvalve is adjusted to flow exhaust gas from the first and second coolersto the exhaust-gas discharge line.
 9. The method of claim 8, wherein thefirst mode occurs in response to an EGR cooling demand being greaterthan or equal to an energy recovery demand, and where the second modeoccurs in response to one or more of the EGR cooling demand being lessthan the energy recovery demand and the EGR cooling demand being lessthan a threshold EGR cooling demand, and where the third mode occurs inresponse to the EGR cooling demand being zero and the energy recoverydemand being greater than zero.
 10. The method of claim 9, wherein thethreshold EGR cooling demand is based on a maximum cooling ability of asingle cooler of the first and second coolers.
 11. The method of claim8, further comprising a fourth mode, where the fourth mode includes notflowing coolant to the first and second coolers of the coolingarrangement, wherein the coolant flows from a coolant system coupled toan engine.
 12. The method of claim 8, wherein the first cooler isadjacent to the second cooler in a single housing, the first coolerbeing fluidly coupled to the exhaust-gas discharge system upstream of athrottle element and to the intake system upstream of a compressor viathe first recirculation line, and where the second cooler is fluidlycoupled to the exhaust-gas discharge system at a location upstream ofthe throttle element and downstream of the first recirculation line viathe second recirculation line, wherein the throttle element is moved toa closed position in each of the first, second, and third modes.
 13. Themethod of claim 12, wherein the exhaust-gas discharge line is fluidlycoupled to a portion of the exhaust-gas discharge system downstream ofthe throttle element.
 14. A system comprising: a cooling arrangementhaving a single housing comprising a first cooler adjacent to andfluidly separated from a second cooler, the first cooler arranged alonga first recirculation line and the second cooler arranged along a secondrecirculation line, wherein the first recirculation line is selectivelycoupled to an intake system via a first control element, wherein thefirst recirculation line and the second recirculation line areselectively coupled to one another via a second control element; asingle coolant system configured to flow coolant to the first and secondcoolers separately; and a controller with computer-readable instructionsstored on non-transitory memory thereof that when executed enable thecontroller to: flow exhaust-gas to the first and second coolers inresponse to an exhaust-gas recirculate cooling demand being greater thanan energy recovery demand during a first mode where the exhaust gas fromeach of the first and second coolers flows to the intake system; flowexhaust gas to the first and second coolers in response to the energyrecovery demand being greater than the exhaust-gas recirculate coolingdemand during a second mode, where the exhaust-gas recirculate coolingdemand is greater than zero, wherein exhaust gas from the first coolerflows to the intake system and exhaust gas from the second cooler flowsto an exhaust-gas-conducting line fluidly coupled to an exhaust-gasdischarge system and flow exhaust gas to one or more of the first andsecond coolers in response to the exhaust-gas recirculate cooling demandbeing zero and the energy recovery demand being greater than zero,wherein exhaust gas from the first and second coolers flows to theexhaust-gas-conducting line via the second control element.
 15. Thesystem of claim 14, wherein the first recirculation line is fluidlycoupled to the exhaust-gas discharge system at a first junction and tothe intake system at a second junction, the second junction furthercomprising the first control element configured to selectively fluidlycouple the first recirculation line to the intake system, where thefirst junction is upstream of the first cooler and the second junctionis downstream of the first cooler, wherein the second recirculation lineis fluidly coupled to the exhaust-gas discharge system at a thirdjunction upstream of the second cooler, and where the secondrecirculation line is fluidly coupled to the first recirculation line ata fourth junction downstream of each of the first and second coolers,and where the second recirculation line further comprises the secondcontrol element arranged at a fifth junction, the fifth junctionarranged downstream of the second cooler, and where the second controlelement selectively fluidly couples the second recirculation line to thefirst recirculation line or to the exhaust-gas-conducting line, andwhere the exhaust-gas-conducting line is fluidly coupled to theexhaust-gas discharge system at a sixth junction, and where the sixthjunction is downstream of each of the first junction, the thirdjunction, and a throttle element.
 16. The system of claim 15, whereinexhaust-gas in the exhaust-gas discharge line flows to only theexhaust-gas discharge system.
 17. The exhaust system of claim 14,wherein the coolant system is further fluidly coupled to an engine. 18.The exhaust system of claim 14, wherein the controller further comprisesinstructions for not flowing coolant to the first cooler and the secondcooler during a fourth mode in response to the exhaust-gas recirculatecooling demand being zero and the energy recovery demand being zero. 19.The exhaust system of claim 14, wherein the first mode further comprisesflowing exhaust-gas to only one of the first or second coolers inresponse to the exhaust-gas recirculate cooling demand being less thanor equal to a threshold exhaust-gas recirculate cooling demand, andwhere the third mode further comprises flowing exhaust gas to only oneof the first or second cooler in response to the energy recovery demandbeing less than or equal to a threshold energy recovery demand, andwhere the threshold exhaust-gas recirculate cooling demand and thethreshold energy recovery demand are based on a maximum cooling abilityof one of the first and second coolers.